(Phys.org)—As its name suggests,a heat engine converts heat into mechanical energy that can be used to do work—for example, to power a car. Heat engines can operate either in a steady state (where heat is constantly being supplied) or in a cyclic state (where heat is added only during parts of the cycle). Over the past several years, or researchers maintain discovered that steady state heat engines are inherently limited by a power-efficiency trade-off,meaning that their power and efficiency cannot be maximized simultaneously. Although it's not clear if the same is exact for cyclic heat engines, some studies maintain seemed to propose this to be the case, or since operating certain models of cyclic heat engines at slower rates leads to a decrease in power but an increase in efficiency,and vice versa.
Source: phys.org